The present invention relates to a liquid crystal display apparatus, a driving device of a liquid crystal display element, and a driving method of the same, and in particular relates to a liquid crystal display apparatus which, through the use of a digitized video signal as an input signal, divides one frame into a plurality of sub-frames and displays images, a driving device of a liquid crystal display element, and a driving method of the same.
The driving method of a liquid crystal display element used for a liquid crystal display apparatus includes an analog method, in which values of voltage applied to a pixel are continuous analog values, and a digital method including the steps of: binarizing the magnitude of a voltage applied to a pixel; and varying the time width of the applied voltage in response to the luminance (gradation) of an image and thereby controlling the effective value of voltage applied to the pixel of a liquid crystal. The digital method is characterized in that it is unlikely to be affected by an external factor such as noise, because only the information of 0 or 1 is applied to a pixel.
In the digital method, a sub-field method is usually used in order to obtain an intermediate gradation. The sub-field method includes the steps of: in one field period of a video signal, preparing a predetermined number of sub-fields in each of which a relative ratio of a drive (light emission) period is varied; appropriately selecting and displaying a sub-field in response to the gradation of a video signal to be displayed; and displaying an intermediate gradation by utilizing a viewer's visual integration effect.
It is known that although, in the sub-field method, a good display image is obtained at the time of displaying a still image, a pseudo contour is generated at the time of displaying a moving image. As a method for solving the pseudo contour, a method for arranging sub-fields is under study that does not cause a change of the center of gravity of light emission as much as possible even if image data varies.
Patent Literature 1 (Japanese Patent Application Laid-Open Publication No. 2006-171651) describes a sub-field method including the steps of: dividing a portion corresponding to higher bits into a plurality of equally-weighted sub-fields; dividing a portion corresponding to lower bits into a plurality of binary-weighted sub-fields; arranging the plurality of binary-weighted sub-fields in the center of one field; dividing the plurality of sub-fields of the portion corresponding to the higher bits into two, respectively; and arranging the resulting sub-fields on both sides of the plurality of binary-weighted sub-fields.
Meanwhile, along with an increase in resolution, an increase in contrast and the like in the recent image display apparatuses, the pseudo contour at the time of displaying a moving image needs to be further reduced.